Apparatus for transmission and reception



1936- R. L. STEINBERGER 2,033,950

APPARATUS FOR TRANSMISSION AND RECEPTION Filed Dec. 4, 1951 2 Sheets-Sheet l FIG. 5

INVENTOB RAYMOND L. ST El NBERGER BY w ATTORNEY 1936. R. STEINBERGER I I APPARATUS FOR TRANSMISSION AND RECEPTION- 2 Sheets-Sheet 2 Filed Dec. 4, 1931 INVENTOR RAYMOND L. STEINBERGER BY W fl ATTORNEY say, they will be in phase.

Patented Dec. 15, 1936 APPARATUS FOR TRANSMISSION AND RECEPTION Raymond Leonard Steinberger, Westwood, Mass., assignor to George W. Pierce, Cambridge, Mass.

Application December 4, 1931, Serial No. 579,039

18 Claims. (cl. 177-386) The present invention, although having fields of more general usefulness, is particularly related ;to devices for converting or translating acoustic energy into electric energy and vice versa. From a more limited aspect, the invention relates to diaphragms.

It has long been recognized, for theoretical 1 reasons which need not be entered into here, that the ideal coupling element for radiating a concentrated beam of acoustic energy into a liquid or gaseous medium, or for the directionally-selective reception of acoustical energy from such a medium in electro-acoustic energy-converter systems, is a diaphragm whose face dimensions are relatively large compared to the wave length of the acoustic energy in the medium, and in which 'all points of the radiating face are vibrating in phase and with equal amplitude like a piston. 20 The ordinary metal membrane diaphragm commonly used at the present time in the communication art, does not satisfy this ideal condition. It cannot move as a piston because it is clamped along it periphery. Such a diaphragm may introduce a dispersion of the radiated energy at its several higher modes of vibration which will cause the various parts of thev diaphragm to be out of phase with one another so that the radiated or received acoustic energy. At the very In the ordinary diaphragm clamped along its periphery and vibrating in its fundamental mode, all portions of the diaphragm will be moving in the same direction at any given time; that is to In the diaphragm described in the present application, the median plane, parallel to and midway between the faces of thediaphragm, executes no appreciable motion along the axis of the diaphragm; that is,-

I 55 by making the thickness of the diaphragm. that is, the length along the axis, substantially equal to one-half of the wave length of sound in the material comprising. the diaphragm. The vibration of the diaphragm in this manner will hereinafter be defined as expansional vibration.

Any longitudinal element of the diaphragm along the axis is, therefore, contracting and expanding along and parallel to the axis. The central, nodal portion 'of the diaphragm, which has no longitudinal motion, nevertheless, at the same time expands and contracts in the nodal plane perpendicular to the axis. It is to permit this transverse motion in the nodal plane that the diaphragm is subdivided in the manner described below.

An object of the present invention is to provide a very sensitive, energy converter of the above-described character that shall translate acoustic into electric energy or vice versa, with greater efficiency than has been possible heretofore.

A further object is to provide a new and improved acoustic piston. This piston will, hereinafter, in the specification and the claims, for convenience and by analogy, be referred to as a diaphragm".

A further object is to provide a sectional diaphragm, the sections or blocks of which are properly designed and individually driven in unison so as to cause the diaphragm to move as a unit expansionally.

A further object is to provide a sectional diaphragm, the sections or blocks of which are permitted a transverse dilation and contraction as they execute a longitudinal contraction and expansion along their axis.

A further object is to provide a novel expansional metal diaphragm.

Another object is to provide a novel diaphragm energized by driving members which are operative through temal stresses, such as are brought about by magnetostriction, or piezo-electricity.

Another object is to provide a novel diaphragm particularly adapted for supersonic electro-acoustic energy conversions.

Other objects will be explained hereinafter, and will be more particularly pointed out in the appended claims.

The invention will be explained in connection with the accompanying drawings, in which Fig. l is a plan of a preferred embodiment of the piston diaphragm of the present invention; Fig. 2 is a section taken upon the line 22 of Fig. 1, looking in the direction of the arrows; Fig. 3 is a perspective upon a larger scale, one of the magnetobeing shown in section; Fig. 4 is a similar perspective of a modification; and Fig. 5 is a diagrammatic view of circuits and apparatus illustrating one form of the invention as applied to piezo-electric-crystal drive.

The invention is illustrated in the accompanying drawings as applied, to a supersonic transmitter or receiver, but it will be obvious that the invention is not limited thereto, and is applicable to other types of transmitters as well as to receivers. The device, if tobe used under water,

may be mounted in a rotatable, submerged hous- A uniform, metallic connection is thus obtained between the outer ring 2 and the diaphragm d. Theweb 6 is thin enough so as to be relatively yielding, thus permitting the receiving or radiating face i of the diaphragm portion 4 to vibrate substantially like a piston, in a direction transversely of itself, substantially all the flexing taking place in the web 6. The large mass of the inertia ring 2 prevents transmission of vibration thereto.

All points on the upper and lower end faces of the single expanslonal, resonant, cylindrical units of which the diaphragm is built, which individual units should have as large a diameter and as small a length as possible, should vibrate in phase over, each face. The limit in choosing a large cross-sectional area compared to axial length, however, is small, because the cylinder has a tendency to vibrate, not only according to its fundamental, but also according to many higher modes of vibration, with resulting nodal lines on its lower, emitting face i. This phenomenon is enhanced owing to the fact that, if the diameter of the diaphragm is large compared to its axial length, the necessary transverse vibration of the diaphragm material in its median planeis restricted. Parts of this face, therefore,

, have a tendency to vibrate in a phase opposite to that of other parts. At a distance from the transmitting face I, therefore, the vibrations set up fromthe transmitting face i in the medium would cancel each other, so that the diaphragm will not emc'iently emit a focused beam of sound energy. These considerations are particularly potent at high frequencies.

The diaphragm portion 4 illustrated in Figs. 1, 2, 3 and 4 is therefore divided into sections or blocks. According to the embodiment of the invention-there illustrated, these blocks are of two kinds: a central, inner, cylindrical or disc-like block a and seven outer blocks in, each in the also be employed.

The sector sections or blocks III are integrally connected to one another by .relatively thin, radially disposed webs l2. located at ornear .the

aocacco strictive-driving elements and an energizing coil axial upper and lower extremities of the blocks,

' mechanically coupled together so that, though it is possible to drive them individually, each of the opposite faces 7 and 9 of diaphragm 4 will vibrate as a piston with the faces I and 9 cpposed in phase. Diaphragms .of this kind may be manufactured conveniently by casting.

The diaphragm ii is in this manner separated into eight resonant blocks, and the spaces between the webs !2 and i3 permit the median nodal sections of the individual blocks to vibrate transversely independently of each other, without having any block react unfavorably upon any of the others and without, therefore, introducing vibrations of different phase in the various por tions of the radiating face i. These spaces between the webs l2 and those between the webs l3 should not be very wide for this purpose, the desirable minimum transverse width of the spaces being determined rather by considerations of easy casting.

As the diaphragm sections vibrate expansionally, as before described, there is a node of iongitudinal motion about half way between their faces I! and 9 and loops of longitudinal motion at the said faces. It will thus be observed that the diaphragm sections are supported by the annular web 6 near these loops of motion.

According to the preferred embodiment of the invention, the driving of the individual blocks 8 and I0 is effected magnetostrictively. To this end, each of the diaphragm blocks 8 and i0 is provided with a magnetostrictive core id, so as to cause individual driving of the blocks 8 and it. The cores It may, of course, be replaced by piezoelectric crystals 25, as shown in Fig. 5, or the blocks may be driven in any other desired manner. When operated magnetostrictively or piezo-electrically, the blocks 8 and iii are driven by means of reversible internal stresses to obtain high frequencies. The cores it may be constituted of 'any desired magnetostrictive material. A thin,

nickel tube, resonant with the blocks 8 and it) to which it is attached, operates very well in practice. To the lower end may be rigidly attached an interiorly threaded cap plate it by means of which the core may be threaded upon a screw 3 that is integrally fixed to the diaphragm blocks 8 and ill. The cores it may be individually and simultaneously caused to vibrate by means of energizing coils, one of which is shown at 20, and supplied with power from any desired source. These coils may also supply a, constant magnetic polarization to the core. The vibrations of the core it are of such a nature that it executes longitudinal expansion and contractions, the free and attached ends being in motion while there will be one or more nodes suitably disposed along the core. The vibrations of the lower extremity ;of the core I l will be communicated to the block 8 or Ill to which it is attached, and the block in. turn will also vibrate expansionally, the degree of vibration depending upon how close it approaches resonance to the driving frequency and to the resonant frequency of the core l4, and upon the magnitude of the internal frictional losses. Theoretically, the core i4 and the block to which it is secured should have substantially the .same natural frequency. No mass other than that of the nickel tube itself is necessary for the vibration of the tube to react against. The, purpose of the cap plate I6 is to provide a convenient means of rigid at I.

tubes it constitute a series of values given by the equation ees) where v is the longitudinal velocity of sound in the metal of the tube, f is the resonant driving frequency, is is any odd integer, while which is independent of L, is determined by the mass of the threaded cap in a manner shown by the equationmo being the mass per unit length of the tube and M the total mass of the cap. From the equation for L, we see that successive optimum values are obtained by starting with the shortest value i (21r 4) 7 when lc=l and increasing the length of this value by successive additions of krepresenting the wave length.

By proper design of the sections 8 and III, the

cores l4 and the coils 20, and by having the current in the coils 20 in phase, the blocks 8 and ill will be caused to be driven in unison, with the result that the emitting face 1 of the diaphragm 4 will be caused to vibrate as a unit at the resonant frequency, say 30 kilocycles, its motion very closely approximating to a true piston motion. The webs l2 and I3 are made short so that they have no possible mode of vibration as low as 30 kilocycles. In this manner, they will introduce no disturbing modes of vibration into the face I of the diaphragm as a whole. The diaphragm 6, therefore, presents to the medium,

such as water, a substantially plane face I, all parts of which are in time phase.

The parts may be varied in design according to the purpose in hand. As shown in Fig. 4,

an additional ring of sectors I5 may be interposed between the sectors l and the ring 2, separated by a web I! similar to the web 6. The diaphragm will still consist of a compressional head, operating in the same manner as before described. It is preferred to make the diaphragm of metal having small mechanical viscosity. Aluminum has a low viscosity, its elastic losses and its decrement are low and it yields a very satisfactory diaphragm.

The operation of the diaphragm may be improved by a composition of cast aluminum with about silicon. The silicon, though not materially affecting the vibrational qualities, lowers the melting temperature and, therefore, facilitates foundry manipulation.

It is desirable to present as large a vibrating surface to the medium as possible with the least complexity of design. The individual blocks or sections it) and 8 should, therefore, have as large an emitting surface I as possible. The metal of the diaphragm should, therefore, preferably be such that the bulk velocity of sound therein is large. Aluminum, besides having a low mechanical viscosity, has also a large bulk velocity of transmission of sound.

It is possible to compute the most suitable dimensions for the blocks. For a cylindrical block, such as the block 8, the practical minimum limit of length to radius of block cross section is about 3 to 1 for all frequencies. If the ratio is much less than this, the block will not vibrate in a simple manner, as before described, but a series of nodal lines will appear upon the radiating face due to the restriction of the necessary lateral vibration in the median plane. The same ratio applies approximately for rectangular and sector blocks, replacing the radius by half the side of the square section 'or half the mean arc width of the sector. The length is determined by the frequency desired and the bulk velocity of sound in the material of the block. For aluminum blocks,lthe following dimensions are found convenient at 30 kilocycles:

a=1 inch, approximately,

L=3 inches, approximately,

where a is the radius of the block 8 or half the mean arc width of the cross-sectional area of the block l0; and L is the height of the blocks. The ratio of the length to the width is thus not substantially less than 3/2.

The resonant frequencies of two short cylinders equal in length whose section areas are equal, one of which is circular and the other square, are nearly, but not quite, equal. If the number of sector blocks I0 is properly chosen, their areas will not differ greatly from the area of the central block 8. By proper design, the areas of the blocks 8 and [0 may be made exactly equal, with the ratio of mean arc width to radial thickness nearly equal to unity for each of the sector blocks. This approximation to unity ratio depends upon the number of blocks per annulus, and becomes the better the larger the mean radius of the annulus. In designing the diaphragm, the number of whole blocks in the given annulus is computed. The departure from the unity ratio of width to thickness necessary in making the cross-section areas equal introduces a negligible error in the frequency computation.

It is found, however, because'of the difference in shape between the block 8 and the block In and because of the loading effect of the webs 6, l2 and i3, that the height of the block 8 may, under certain conditions, be slightly different from that of the blocks Ill, else the frequency of the central block 8 will be slightly different than that of the other blocks ID. The exact design cannot readily be worked out mathematically, but may best be checked experimentally. In Fig. 3, the central block 8 is shown slightly shorter in length than the annular blocks ID and the upper faces of the webs l2 and i 3 are disposed in the same plane with the upper face of the central sector 8. These webs must not, of course, be positioned lower down, at a point of nodal expansion and contraction, but could be positioned elsewhere.

The frequency of a longitudinally-vibrating bar can be computed even when the ratio of radius of the cross-section to the length becomes large by making a suitable correction for radial inertia. 1f the length is not large compared with the diameter of the bar, the expression for the frequency of longitudinal resonance of a short thick bar of elliptical or rectangular cross-sec tion as given by Chree, Quart. Math.- Journal, Vol. 23, p.317, 1889, becomes 1: E wkP K nt/{ 477 2] density, P is Poissons ratio normally taken as 1/3, and K is the radius of gyration of the section about the cylindrical axis.-

The above equation is also valid for the case where K/L'is small. Then it reduces to which is the familiar formula for the frequency of longitudinal vibrations in a slender bar.

The difference between this latter formula and the more accurate formula given by Chree for the general case is a small correction term about 3% for bars in which the ratio of radius'of cross-section or half side of rectangular section to the length is about 1:3.

The ratio E/d which is the square of the bulk velocity may be computed after experiments performed upon the specific material used and the result employed in connection with the computation of new vibrators of that material.

Using these-formulas for the block frequencies,

' it will be found that if a=1 inch, as above, the corresponding length of the aluminum central block 8, as determined for a BO-kilocycle frequency is L= 3.2 inches. This is a very fair approximation of the 3 to 1 ratio before mentioned. -In practice, however, good results may be obtained if the ratio is as great as, or even greater than, 20 to 1. The thickness of the diaphragm is equal to a halfwave length of sound in the material thereof, or to integral multiples of the half-wave length.

These dimensions are suitable for a 30-kilocycle frequency. To increase the area of the sound-emitting plane surface "I at this frequency, it is preferable to add additional annuli 22 of sector blocks between the annulus blocks l and Y the fixed annular portion 2, as shown in Fig. 4.

'According to the modification illustrated in Fig. 5, each of the blocks is driven by a piezoelectric crystal 24 rigidly fastened at one end by means of suitable cement tothe upper face 9 of theblock. The crystal electrodes may consist of-tin-foil layers 26 deposited upon opposite faces of the crystal, but any other electrodes of suitable 'type may be, employed. The tin-foil layers or other electrodes may b connected by conductors 28 in parallel to a coil 30coupled to a coil 32 in the output circuit of a vacuum-tube oscillator 36 or of any other source of alternating-current frequency. The frequency of the output of this oscillator may be adjusted by means of a tuning condenser 36. A further condenser 38 in parallel with the crystal vibrators 24 may be employed to adjust the voltage on the crystals.

It will be understood that the invention is not restricted to the illustrated embodiments thereof, but is susceptible to further modifications and change withinv the skillof the artisan, and all a accaeco between the faces, whereby the said one face may vibrate between limiting positions on both sides of the position of rest occupied by the said one face when the diaphragm is at rest, and means positioned near the said position of rest of the said one face in a region substantially removed from the said node and aside from the path of .vibration of the said one face for supporting the diaphragm.

2. A device of the class described comprising a diaphragm having two oppositely disposed faces one of which is adapted to be disposed in a medium, the diaphragm being adapted to be vibrated in the medium so as to produce a loop of motion at the said one face with substantial phase equality over the face, and a node of motion between the faces, at a frequency such that the dimensions of the said one face are large compared to the wave length of acoustic energy in the medium, the said one face vibrating about the posetion of rest occupied by the said one face when .the diaphragm is atrest, and means positioned in substantially the plane of the said position of rest of the said one face and aside from the path of vibration of the said one face for supporting thediaphragm.

3. A device of the class described comprising a diaphragm having two oppositely disposed faces and adapted to vibrate expansionally by contracting and expanding to and from a nodal plane disposed intermediately between the faces to produce a loop of expansional vibration at one of the faces, whereby the said one face may vibrate between limiting positions on both sides of the position of rest occupied by the said one face when the diaphragm is at rest, and means positioned near the said position of rest of the said one face in a region substantially removed from the said nodal plane and aside from the-path of vibration of the said one face for supporting the diaphragm.

4. A device of the class described comprising a diaphragm having two oppositely disposed faces the distance between which is substantially equal to a half-wave length or integral multiples of a half-wave length of sound in the material of which the diaphragm is constituted, the diaphragm being adapted to vibrate expansionally by contracting and expanding to and from a nodal plane disposed intermediately between the faces between limiting positions on both sides of the positions of rest occupied by the said faces when the diaphragm is at rest, and means positioned near the said position of rest of one of the said faces in 'a region substantially removed from i the said nodal plane and aside from the path of expansional vibration for supporting the diaphragm.

5. A device of the class described comprising a. vibratory portion having two oppositely disposed faces and adapted to vibrate so as to produce-a loop of motion at one of the faces and a node of motion between the faces, whereby the said one face may vibrate between limiting positions on both sldesof the position of rest occupied by the said one face when the vibratory portion is at rest, a relatively fixed portion positioned near the said'position of rest of the said one face in a region substantially removed from the said node and aside from the path of vibration of the said one face for supporting the vibratory portion, and an intermediately disposed web connecting the portions andthrough which the vibratory portion is supported by the relatively fixed portion.

6. A device of the class described comprising a vibratory portion having two oppositely disposed faces and adapted to vibrate expansionally by contracting and expanding to and from a nodal plane disposed intermediately between the faces to produce a loop of expansional vibration at oneof the faces, whereby the said one face may vibrate between limiting positions on both sides of the position of rest occupied by the said one face when the vibratory portion is at rest, a relatively fixed portion positioned near the said position of rest of the said one face in a region substantially removed from the said nodal plane and aside from the path of vibration of the said ,tion.

7 A device of the class described comprising a.

diaphragm having two oppositely disposed faces one of which is adapted to be disposed in a medium .to constitute a radiating or receiving face, the diaphragm being adapted to be vibrated in the medium so as to produce a loop of motion at the radiating or receiving face and a node of motion between the faces, whereby the radiating or receiving face may vibrate between limiting positions on both sides of the position of rest occupied by the radiating or receiving face when the diaphragm is at rest, a support positioned near the said position of rest of the radiating or receiving face in a region substantially removed from the said node and aside from the path of vibration of the radiating or receiving face, and a web connecting the diaphragm near the radiating or receiving face with the support.

8. A device of the class described comprising a metal diaphragm, the metal of the diaphragm having only a small viscosity, the diaphragm having two oppositely disposed faces and being adapted to vibrate so as to produce a loop of motion at one of the faces and a node of motion between the faces, whereby the said one face may vibrate between limiting positions on both sides of the position of rest occupied by the said one face when the diaphragm is at rest, and means positioned near the said position of rest of the said one face in aregion substantially removed from the said node and aside from the path of vibration of the said one face for supporting the diaphragm.

9. A device of the class described comprising a diaphragm having two oppositely disposed faces adapted to vibrate toward and away from an intermediately disposed nodal plane, and means positioned near one of the faces in a region substantially removed from the said nodal plane and aside from the path of vibration of the 'said face for supporting the diaphragm.

10. A diaphragm having two oppositely disposed faces and dimensioned to vibrate expansionally in longitudinal resonance with a predetermined frequency about a nodal plane intermediately disposed between said faces, and a web afilxed to the diaphragm at the border of one of said faces for supporting the diaphragm.

11. A diaphragm having a relatively fixed portion, awibratory portion provided with a rabetween the faces, the relatively fixed portion constituting a support for the vibratory portion, and a web integrally connecting the portions, the web being disposed near the radiating or receiving face in a region substantially removed from the said node and at a substantial distance from the said opposite face.

12. Apparatus of the character described comprising a resonant expansionally vibratory diaphragmhaving two oppositely disposed faces, means for supporting the diaphragm comprising a relatively fixed support and aweb connecting the support and the diaphragm, the web being affixed to the diaphragm in substantially coplanar relation with one of the said faces, and means for reciprocally vibrating the faces toward and from each other.

13. A vibrator for interchanging electrical and mechanical energy with a sound-conveying medium comprising a plurality of diaphragm sections having substantially the same natural frequency and adapted to be positioned in sonorous relation to the sound-conveying medium, the sections being adapted to vibrate expansionally by contracting and expanding lengthwise to and from intermediately disposed nodal planes, the sections being spaced from each other transversely at the nodal planes so as to be free to expand and contract transversely at the nodal planes during their expansional vibration, and means localized near a loop of vibration and connecting the sections for supporting the sections and cophasing their vibration's.

14. A vibrator for interchanging electrical and mechanical energy with a sound-conveying medium and having inner and outer faces, a plurality of diaphragm sections connecting the inner and outer faces and having substantially the same natural frequency, the outer face being adapted to be positioned in sonorous relation to the sound-conveying medium, the diaphragm sections being adapted to vibrate expansionally at substantially the said frequency to cause them to contract and expand lengthwise to and from a plane disposed between the inner and outer faces, whereby loops of vibration occur at the inner and outer faces and a node of vibration occurs at the intermediately disposed plane, the sections covering substantially the whole area of the inner and outer faces but being very slight- 1y spaced fromeach other transversely so as to be free to contract and expand transversely at the nodal plane during their expansional vibration.

15. A device of the class described having a vibratory diaphragm portion and a relatively fixed portion, the vibratory portion comprising a plurality of diaphragm sections, each section having two oppositely disposed faces and being adapted to vibrate expansionally by contracting and expanding toward and from an intermediately disposed nodal plane, one set of the section faces being disposed in a single plane, and means interconnecting the plurality of sections with each other and with the said relati ely fixed portion, affixed to the individual sections near the said coplanar faces and aside from .he path of vibration in the sections, for cophasing the vibrations and supporting the sections.

16. A vibrator for interchanging electrical and mechanical energy with a sound-conveying medium comprising a diaphragm having two oppositely disposed faces one of which is adapted to be disposed in the medium, the diaphragm being subdivided for part of its thickness by channels to produce 'a plurality of diaphragm sections having substantially the same natural frequency, and the sections being adapted to vibrate expansionally by contracting and expanding lengthwise to and from nodal planes disposed between the faces to. produce a loop of motion at the said one face with substantial phase equality over the said one face.

17. A vibrator for interchanging electrical and mechanical energy with a sound-conveying medium comprising a diaphragm having two oppositelydisposed faces one of which is adapted to be disposed in the medium, the diaphragm being subdivided for part of its thickness by channels to produce a plurality of diaphragm sections having substantially the-same natural frequency, the

sections being adapted to vibrate expansionally by contracting and expanding lengthwise to and from .nodal planes disposed between the faces to produce a loop of motion at the said one face with substantial phase equality over the said one face, whereby the said one face may vibrate beaoeacto tween limiting positions on both sides or a position of rest occupied by the said one face when the diaphragm is at rest, and means positioned near the said position of rest of the said one face in a region substantially removed from the said nodal planes and aside from the path of vibration of the said one face for supporting the diaphragm. l

18. A diaphragm having a fixed outer portion, a vibratory inner diaphragm portion, an intermediately disposed web connecting the portions, the diaphragm portion comprising a plurality of diaphragm sections connected together by webs, each section having two oppositely disposed faces and being adapted to vibrate expansionally by contracting and expanding to and from a nodal RAYMONl) L. STEINBERGER. 

